MICROSCOPIC OBJECTS. 67 



plates of glass, under a power of 50 or 60 diameters. The 

 varied pores and beautiful concentric circles around them 

 may be readily seen. g^ 



Wings of Butterflies, 8fC. — " In the^election of the 

 wdngs of insects given in the Ust, I have introduced many 

 which require to be mounted in Canada balsam, in order 

 to render them sufficiently diaphanous to be examined 

 as transparent objects. The larger wings, when entire, 

 are especially suited to the oxyhydrogen or solar micro- 

 scope. Here instruction and amusement might go hand 

 in hand : a wing from each order of insects might be 

 placed in one slide in such a position that by using a low 

 power the whole of them might be exhibited on the 

 screen at one view, and by their characteristic differ- 

 ences being thus brought into apposition their distinc- 

 tion might be permanently stamped upon the mind." — 

 Pritchard's List, p. 1 1 . 



The transparent wing of the Hemerobius is admirably 

 adapted for exhibiting, in the Hving state, the circulation 

 in its nervures. The tubular structm-e of the nervures 

 is often distinctly seen in wings mounted in Canada bal- 

 sam, those parts of them which are injected being trans- 

 parent, while the parts filled with air appear dark at the 

 sides. 



The ocellus or eye-like spot from the wing of the 

 Emperor Moth is interesting as showing the concentric 

 arrangement of the scales upon the membrane of the 

 wing. (Power 30 diameters.) The form of the scales 

 and their markings, which may be seen in situ when that 



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